What good is a notebook that dies two hours after it's unplugged from the wall? Not much. We've created a list of the clamshells that ran the distance on the LAPTOP Battery Test (continuous web surfing over Wi-Fi). Each machine lasts (at least) to the 7-hour marker, but some systems use larger, sold-separately batteries to stay active up to 20 hours. See for your yourself below.

Looking for a battery that can make it through the day without having to be tied to a power outlet? Laptop Magazine's Kenneth Butler has you covered with his rundown of 10 long-lasting laptops.

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Lenovo ThinkPad X230

Consider the Lenovo ThinkPad X230 the poster-laptop for systems with optional batteries. The 12-inch ultraportable ships with a 6-cell battery that lasts a decent 7 hours, but the sold-separately 9-cell option pushes the juice supply beyond the 12-hour mark. If that's not enough productivity time for you, the X230 also works with a sheet-battery that, when paired with the 9-cell, helped the system run an epic 20 hours! [Review]

Lenovo ThinkPad T430

When configuring the ThinkPad T430, you'll have to pay an extra $50 to upgrade to a 9-cell battery, but considering that this notebook has the best keyboard you can get, you'll want to use it all day long and then some. With it's extended battery aboard, this powerful portable lasts a whopping 13 hours and 25 minutes. [Review]

Lenovo ThinkPad Carbon X1

For its $1,249 starting price, the 3-pound, .76-inch thick Lenovo ThinkPad Carbon X1 comes with some impressive specs, including a fast Core i5 CPU, a durable carbon roll cage, and a 14-inch matte screen with a 1600 x 900 resolution that offers brighter whites than the MacBook Air. Best of all, the sealed-in battery provides a strong 7 hours and 45 minutes of endurance. [Review]

Dell Latitude E6430

For a 14-inch notebook with more than one type of staying power, the durable Dell Latitude E6430 is a solid choice. We say that not only because of its Tri-Metal frame (made of magnesium alloy, steel hinges, and chrome bumpers), its spill-resistant keyboard, and its MIL-STD 810G-level resistance to degrees, dust, and drops, but also for the 10 hour and 37 minutes the E6430's 9-cell battery provided during our tests. That battery option costs an additional $79 bucks, but durability and long battery life like this is worth the extra cash. [Review]

Sony VAIO SE

Sure, the Sony VAIO SE's sheet battery adds $150 to the media-friendly notebook's $929 starting price, not to mention 1.3 pounds to its lightweight 4.4-pound frame, but with 10 hours and 35 minutes of portable power, the added cash and heft are worth it. The battery sheet will go a long way toward helping you watch beautiful movies and video on that 1920 x 1080, matte display, all without the need to plug into a power outlet. [Review]

Dell XPS 14

Meet one of the beefiest Ultrabooks on the block. The thick-sided Dell XPS 14 weighs a whopping 4.8 pounds (about a pound or two heavier than many other Ultrabooks). Sometimes, though, the heaviest loads bear the most fruit. A bulky 64-watt battery supplies the XPS 14's added heft, but lifts this 14-inch notebook to a battery life of 8 hours and 14 minutes, a result that outlasts much of the Ultrabook competition, including (just slightly) the Apple MacBook Air (8:10). [Review]

Apple MacBook Air

The Apple MacBook Air just gets better and better. Not only does the 2012 model max out with a battery life of 8 hours and 10 minutes, but it also packs a faster Intel processor, adds USB 3.0 ports, boasts gaming-worthy integrated graphics, and costs $100 bucks less than the previous model.

All those improvements fit into the same compact, 3-pound, single-body aluminum chassis, giving notebooks buyers a standard-bearing ultraportable with a sweet exterior, performance-minded hardware and enough battery life for the road. [Review]

Apple MacBook Pro with Retina Display

Apple provided several impressive hardware tweaks on the latest MacBook Pro. The most noticable is the 2880 x 1800-pixel Retina Display, which tallies up to more than 5 million pixels on a 15-inch panel.

What kind of battery can power a screen like that for 8 hours? Apple ditched the mechanical drive in older MacBook Pro's in favor of flash memory, then used the extra space to shoehorn in a larger 95-watt hour battery (up from 77.5-watt hours in the previous model). The result? A long-lasting system with enough juice to power the best 15-inch display we've ever seen for 8 hours and 2 minutes .[Review]

Toshiba Portege R835

It's not the slimmest ultraportable on the store shelf, but the Toshiba Portege R835 packs power and performance for any working professional in need of a travel-ready laptop. For $799, the system ships with Core i5 power, 4GB of RAM, a 640GB hard drive, and a battery that lasted 7 hours and 35 minutes on the LAPTOP Battery Test. [Review]

Acer Aspire TimelineU M5-581TG-6666

If it's a thin, powerful, and long-lasting PC you're looking for, Acer Aspire TimelineU M5-581TG-6666 firs the bill. This 15.6-inch media-minded laptop lasted 7 hours and 29 minutes on a charge, and, for $829, includes a low-voltage Core i5 processor, 6GB of RAM, a 500GB hard drive and Nvidia GT 640M LE graphics that helped it wipe out the competition on our graphics benchmarks. What's more, all that performance and power comes in a chassis that's just .81-inches thin.[Review]